substrate manufacturing equipment

Abstract

To provide a technique to reduce the surface roughness of a substrate separated from an ingot.SOLUTION: A substrate manufacturing device comprises a stage on which a semiconductor substrate is disposed. The substrate manufacturing device comprises an irradiation unit which can irradiate the semiconductor substrate disposed on the stage with a pulsed laser of a predetermined pulse period. The substrate manufacturing device comprises a control unit which can control the relative position between the stage and the irradiation unit. The irradiation unit can generate a plurality of condensing points arranged side by side on a straight line at a predetermined pitch. The control unit can move the relative position between the stage and the irradiation unit at a predetermined speed, in parallel to the straight line on which the plurality of condensing points are arranged side by side. The predetermined speed is a speed at which the distance the plurality of condensing points moves in one period of the predetermined pulse period becomes the same as the predetermined pitch.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This specification discloses a technique related to a substrate manufacturing apparatus. [Background technology]

[0002] Patent Document 1 discloses a method for producing a gallium nitride substrate from a gallium nitride ingot. Specifically, a modified region in which gallium and nitrogen are precipitated is formed by irradiating a gallium nitride ingot at a certain depth inside the ingot while scanning the focal point of a pulsed laser at a constant speed. A large number of modified regions are formed on a flat surface, forming an interface. The ingot is heated to a temperature at which gallium melts, and a first holding member and a second holding member are moved in directions away from each other, thereby separating the ingot from the interface and producing a gallium nitride substrate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-57103 Summary of the Invention [Problem to be solved by the invention]

[0004] To reliably form a modified region, it is necessary to increase the total amount of energy applied to the irradiation point. However, if the laser output is increased, a large amount of energy is applied to the irradiation point in a single irradiation, which may cause unintended cracks, etc. The surface roughness of the separated gallium nitride substrate will increase. [Means for solving the problem]

[0005] This specification discloses a substrate manufacturing apparatus. The substrate manufacturing apparatus includes a stage on which a semiconductor substrate can be placed. The substrate manufacturing apparatus includes an irradiation unit that can irradiate the semiconductor substrate placed on the stage with a pulsed laser at a predetermined pulse period. The substrate manufacturing apparatus includes a control unit that can control the relative position between the stage and the irradiation unit. The irradiation unit is capable of generating multiple focal points that are arranged in a straight line at a predetermined pitch. The control unit is capable of moving the relative position between the stage and the irradiation unit at a predetermined speed parallel to the line on which the multiple focal points are arranged. The predetermined speed is a speed at which the distance that the multiple focal points move in one cycle of the predetermined pulse period is the same as the predetermined pitch.

[0006] In the substrate manufacturing apparatus of this specification, multiple focal points are moved in a linear direction in which the multiple focal points are arranged. The distance that the multiple focal points move in one cycle of a predetermined pulse period is the same as the predetermined pitch. This allows multiple focal points of the pulse laser to irradiate the same irradiation point. Therefore, energy can be applied to the same irradiation point multiple times using the multiple focal points. Compared to applying energy to the irradiation point in a single irradiation, the total amount of energy applied can be kept equal to or greater than that of the case where energy is applied to the irradiation point in a single irradiation, while the laser output per irradiation can be reduced. This makes it possible to suppress the occurrence of unintended cracks, etc.

[0007] The irradiation unit may include a plurality of laser light sources, and a plurality of light-focusing points may be generated by the plurality of laser light sources.

[0008] The pulse energy of some of the plurality of focal points may be different from the pulse energy of the other focal points.

[0009] Of the plurality of focal points, the pulse energy of a focal point on the front side in the traveling direction in which the control unit moves the plurality of focal points may be smaller than the pulse energy of a focal point on the rear side in the traveling direction.

[0010] Of the plurality of focal points, the pulse energy of a focal point on the front side in the traveling direction in which the control unit moves the plurality of focal points may be greater than the pulse energy of a focal point on the rear side in the traveling direction.

[0011] The pulse width of some of the plurality of focal points may be different from the pulse width of the other focal points.

[0012] Of the plurality of focusing points, the pulse width of the focusing point on the front side in the traveling direction in which the control unit moves the plurality of focusing points may be smaller than the pulse width of the focusing point on the rear side in the traveling direction.

[0013] Of the plurality of focusing points, the pulse width of the focusing point on the front side in the traveling direction in which the control unit moves the plurality of focusing points may be greater than the pulse width of the focusing point on the rear side in the traveling direction.

[0014] The wavelengths of some of the plurality of light-focusing points may be different from the wavelengths of the other light-focusing points.

[0015] Of the plurality of focusing points, the wavelength of the focusing point on the front side in the traveling direction in which the control unit moves the plurality of focusing points may be greater than the wavelength of the focusing point on the rear side in the traveling direction.

[0016] Of the plurality of focusing points, the wavelength of the focusing point on the front side in the traveling direction in which the control unit moves the plurality of focusing points may be shorter than the wavelength of the focusing point on the rear side in the traveling direction.

[0017] The irradiation unit may further include a measurement unit that measures the modified region formed on the semiconductor substrate on the stage using the plurality of focusing points, and the irradiation unit may control the number of the plurality of focusing points according to the measurement results by the measurement unit.

[0018] The measurement unit may be capable of measuring the size of the modified region. The irradiation unit may be controlled so that the number of the plurality of light-focusing points increases as the size of the modified region decreases. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a schematic configuration diagram of a substrate manufacturing apparatus 1 according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view showing light-converging points P1 to P6. [Figure 3] FIG. 2 is a schematic diagram of scanning lines SL1 to SL6. [Figure 4] FIG. 10 is a diagram showing how the light-converging points P1 to P6 move. [Figure 5] 1 is a flowchart showing a substrate manufacturing method according to a first embodiment. [Figure 6] FIG. 2 is a diagram showing an example of an ingot 30 on which a modified layer is formed. [Figure 7] FIG. 10 is a schematic configuration diagram of a substrate manufacturing apparatus 1a according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION [Example]

[0020] (Configuration of substrate manufacturing apparatus 1) 1 shows a schematic configuration diagram of a substrate manufacturing apparatus 1. The substrate manufacturing apparatus 1 includes a stage driving unit 11, a stage 12, an irradiation unit 13, a measurement unit 14, and a control unit 15. The stage driving unit 11, the irradiation unit 13, and the measurement unit 14 can be controlled by the control unit 15. The control unit 15 is, for example, a PC. An ingot 30 to be processed can be placed on the stage 12.

[0021] The irradiation unit 13 is a portion capable of irradiating the ingot 30 placed on the stage 12 with a pulsed laser having a predetermined pulse period. The irradiation unit 13 includes a laser light source 21, a spatial light modulator 23, and a condenser lens 24. The laser light source 21 is a device that outputs laser light that is transparent to the ingot 30. In this example, a pulsed laser with an oscillation frequency of 50 kHz (i.e., a pulse period of 0.02 ms) was used. The wavelength was 532 nm.

[0022] The spatial light modulator 23 is a device that modulates the phase of the pulsed laser PL output from the laser light source 21. In this embodiment, a spatial light modulator 23 using reflective liquid crystal (LCOS: Liquid Crystal on Silicon) is used. The spatial light modulator 23 can freely shape a light beam pattern. The spatial light modulator 23 can also modulate the pulsed laser PL so that the pulse energy of some of the multiple focusing points differs from the pulse energy of the other focusing points. In this embodiment, the pulsed laser PL is modulated so that six focusing points P1 to P6, which will be described later, are formed. The number of focusing points can be freely changed and is not limited to six. The pulse energy at each focusing point can also be set individually.

[0023] The focusing lens 24 focuses the pulsed laser modulated by the spatial light modulator 23. This allows six focusing points P1 to P6 to be formed at positions a focusing distance FD away from the focusing lens 24. FIG. 2 shows a cross-sectional view of the ingot 30 at a depth where the focusing points P1 to P6 are located. That is, FIG. 2 is a cross-sectional view of the surface where the modified layer L1 is formed. The focusing points P1 to P6 are aligned on a straight line LX extending in the X direction. The focusing points P1 to P6 are aligned at equal intervals at a predetermined pitch PP. In this embodiment, the predetermined pitch PP is 5 μm. The peak output of each of the focusing points P1 to P6 is the same, 0.025 W.

[0024] By controlling the stage driving unit 11 with the control unit 15, it is possible to move the stage 12 in the X, Y, and Z directions. In other words, the control unit 15 can control the relative position of the stage 12 and the irradiation unit 13 with the stage driving unit 11. The measurement unit 14 is a part that measures the numerous modified regions MA formed inside the ingot 30. The modified regions MA will be described later. In this embodiment, the measurement unit 14 is a camera.

[0025] (Scanning of the focal point) As shown in Fig. 3, by controlling the stage driving unit 11 using the control unit 15, the light condensing points P1 to P6 can be caused to scan the scanning lines SL1 to SL6. For each of the scanning lines SL1 to SL6, the light condensing points P1 to P6 in Fig. 2 can be moved in the traveling direction TD, which is the +X direction, by moving the stage 12 in the -X direction. That is, for each of the scanning lines SL1 to SL6, the light condensing points P1 to P6 move on a straight line LX on which the light condensing points P1 to P6 are aligned.

[0026] The scanning lines SL1 to SL6 are scanned at a predetermined speed. The predetermined speed is a speed at which the distance that the focal points P1 to P6 move in one period (0.02 ms) of the pulse laser is the same as the predetermined pitch PP (5 μm). In this embodiment, the predetermined speed is set to 250 mm / s.

[0027] This will be explained using FIG. 4. FIGS. 4(a) to 4(f) show the movement of the focal points P1 to P6 in the propagation direction TD for each pulsed laser cycle. Focus on a specific irradiation point IP. In FIG. 4(a), the focal point P1 irradiates the irradiation point IP with the pulsed laser for the first time. In FIG. 4(b), after one cycle (0.02 ms), the focal point P2 irradiates the irradiation point IP with the pulsed laser for the second time. Similarly, in FIG. 4(f), after five cycles (0.10 ms), the focal point P6 irradiates the irradiation point IP with the pulsed laser for the sixth time. This allows the six focal points P1 to P6 to apply energy six times, forming a modified region MA at the irradiation point IP. That is, the modified region MA can be formed in two steps: a seed formation step in which a small modified region MA (a seed of the modified region MA) is formed, and an expansion step in which the formed modified region MA is expanded. Then, the irradiation points IP can be formed in a state where they are arranged at a predetermined pitch PP (5 μm) on the scanning lines SL1 to SL6.

[0028] As described above, the spatial light modulator 23 can individually set the pulse energy at each of the focal points P1 to P6. Therefore, various pulse energy settings are possible. For example, the pulse energy at the focal points P1 to P6 may be equal (first energy setting). The pulse energy at the focal point on the front side of the traveling direction TD may be lower than the pulse energy at the focal point on the rear side of the traveling direction TD (second energy setting). The pulse energy at the focal point on the front side of the traveling direction TD may be higher than the pulse energy at the focal point on the rear side of the traveling direction TD (third energy setting). Since the peak output [W] is calculated by dividing the pulse energy [J] by the pulse width [s], when the pulse width is constant, the peak output can be increased as the pulse energy increases. With the first energy setting, the integrated amount of energy can be linearly increased at each of the multiple irradiation points IP. With the second energy setting, the integrated amount of energy can be reduced in the first half of irradiation and increased in the second half. In the third energy setting, the energy accumulation amount can be increased in the first half of irradiation and decreased in the second half.

[0029] In the second and third energy settings, the pulse energy may change in various ways. For example, the pulse energy may change linearly toward the front in the traveling direction TD, or the pulse energy may change stepwise for each of the multiple focusing points.

[0030] (Substrate manufacturing method) The substrate manufacturing method according to the first embodiment will be described with reference to the flow chart of Fig. 5. The substrate manufacturing method includes an irradiation step of step S10, a separation step of step S30, and a polishing step of step S40.

[0031] The irradiation step of step S10 will now be described. The irradiation step is a step of forming N modified layers (N is a natural number equal to or greater than 1) in an ingot. FIG. 6 shows an example of an ingot 30 on which modified layers have been formed by the irradiation step. FIG. 6 shows a top view and a side view of the ingot 30. In this example, a case where the number of modified layers is four will be described. The ingot 30 is formed of a single crystal of gallium nitride (GaN). The GaN single crystal is colorless. The ingot 30 has four modified layers L1 to L4 formed at different depths from the surface 30s. The four modified layers L1 to L4 divide the ingot 30 into five substrate layers 31 to 35.

[0032] The modified layer is a layer in which numerous modified regions exist within the XY plane. The modified region is an area in which the density, refractive index, mechanical strength, and other physical properties differ from those of the initial GaN crystal. As will be described later, the modified region is formed when the nitrogen in the GaN becomes gas and evaporates due to localized heating at the focal point of the pulsed laser. Gallium precipitates in the modified region, giving it a black color.

[0033] The irradiation process of step S10 includes steps S11 to S19. In step S11, the modified layer L of the Kth layer (K ​​is a natural number of 1 or more and N or less) is K The height of the stage 12 in the Z direction is adjusted so that the focal point P is located at a depth where the modified layer L1 is formed. In the example of FIG. 1, the lowermost modified layer L1 is formed at a depth D1 from the surface 30s.

[0034] In step S12, one scanning line is scanned (see FIG. 3). In step S13, it is determined whether scanning of all scanning lines has been completed. If a negative determination is made (S13: NO), the process proceeds to step S14. In step S14, it is determined whether a predetermined number of scanning lines (e.g., three) have been scanned. If a negative determination is made (S14: NO), the process returns to step S12, and the next scan is performed. If a positive determination is made (S14: YES), the process proceeds to step S15, and the modified region is measured. This allows the modified region to be measured every time a predetermined number of scans are performed.

[0035] The measurement in step S15 is performed using the measurement unit 14. For example, multiple modified regions MA may be photographed with a camera, and the image may be processed by the control unit 15 to determine the size of each of the multiple modified regions and calculate the average value.

[0036] In step S16, it is determined whether the size of the modified area MA is within a predetermined tolerance. If it is within the tolerance, it is determined that the modified area MA has been properly formed, and the process returns to step S12. The next scan is then performed.

[0037] On the other hand, if the size of the modified region MA is smaller than the allowable range (S16: Small), the process proceeds to step S17. In step S17, the spatial light modulator 23 is adjusted to increase the number of focal points without changing the pulse energy at each focal point. The process then returns to step S12, where the next scan is performed. This allows the integrated amount of energy applied to the modified region MA to be increased in the next and subsequent scans, making it possible to expand the size of the modified region MA.

[0038] If the size of the modified region MA is larger than the allowable range (S16: Large), the process proceeds to step S18. In step S18, the spatial light modulator 23 is adjusted to reduce the number of focal points without changing the pulse energy at each focal point. The process then returns to step S12, where the next scan is performed. This reduces the cumulative amount of energy applied to the modified region MA in the next and subsequent scans, making it possible to reduce the size of the modified region MA.

[0039] The number of light-collecting points to be increased or decreased is not limited to 1. For example, the number may be increased or decreased by two or more depending on the difference between the measured size of the modified region MA and the allowable range.

[0040] When scanning of all the scanning lines is completed, it is determined in step S13 that the scanning is finished (S13: YES), and the process proceeds to step S19.

[0041] In step S19, it is determined whether or not the topmost modified layer has been formed. If the determination is negative (S19: NO), the process proceeds to S20, where the (K+1)th modified layer L K+1 Then, the stage 12 is moved in the −Z direction so that the focal point P moves to a depth where the next modified layer L is formed. K+1 As a result, the modified layers L1 to L4 are formed one by one in order from the bottom up. That is, the modified layers are formed one by one in order from the modified layer L1 located deepest from the surface 30s to the modified layer L4 located shallowest. This makes it possible to prevent the formation of subsequent modified layers from being hindered by the presence of modified layers formed earlier.

[0042] If the topmost modified layer L4 is formed, an affirmative determination is made in step S19 (S19: YES), the irradiation step in step S10 ends, and the process proceeds to step S30.

[0043] In the separation process of step S30, heat and stress are applied to the ingot 30 to propagate cracks extending from the modified regions MA formed in large numbers in the modified layers L1 to L4 in the in-plane direction, thereby separating the substrate layers 31 to 35 of the ingot from each other at the positions where the modified layers L1 to L4 were formed.

[0044] Proceeding to the polishing step of step S40, the front and back surfaces of each of the separated substrate layers 31 to 35 are polished. This removes damaged layers and enables planarization. The polishing step may be performed using, for example, CMP (chemical mechanical polishing).

[0045] (effect) Enlarging the modified region MA has been considered to improve the flatness of the substrate surface formed by separation. Conventional techniques for forming modified region MA by a single laser irradiation require increasing the laser output (i.e., increasing the applied energy). However, increasing the applied energy in a single irradiation is likely to result in the occurrence of massive gallium precipitation and the elevation of the precipitation position. This can lead to cracks and deterioration of the flatness of the substrate surface. The substrate manufacturing apparatus of this specification can apply energy in multiple irradiations using multiple focal points, as described in FIG. 4 . Compared to applying energy in a single irradiation, the energy per irradiation can be reduced while maintaining the same or greater total amount of applied energy. Therefore, the energy of each of the multiple focal points can be reduced to a level that does not cause massive gallium precipitation. Furthermore, by repeatedly applying energy to the same point using multiple focal points, the modified region MA can be gradually formed. It is possible to enlarge the modified region MA while suppressing the occurrence of massive gallium precipitation and the elevation of the precipitation position.

[0046] Even in conventional technology, a modified region MA can be formed by multiple irradiations by controlling the table so that the pulsed laser irradiates the same irradiation point a predetermined number of times and then moves to the next irradiation point. However, such table position control is generally difficult. For example, consider the case in this embodiment where the pulse period is 0.02 ms, the pitch between irradiation points is 5 μm, and the pulsed laser is irradiated six times per irradiation point. In this case, the table must be repeatedly controlled to move 5 μm every 0.1 ms. The movement time is 0.02 ms. This type of position control is difficult and also results in vibration and misalignment. In contrast, in the substrate manufacturing apparatus described herein, the table only needs to be moved at a constant speed. Controlling the table at a constant speed significantly improves positional accuracy compared to the repetitive control described above. Therefore, multiple laser irradiations of the same irradiation point can be performed with high precision.

[0047] When applying energy to GaN through multiple laser irradiations, as described above, the processing can be divided into a seed formation step in which a small modified region MA (a seed of the modified region MA) is formed, and an expansion step in which the formed modified region MA is expanded. Furthermore, if the energy applied in a single laser irradiation exceeds a certain energy threshold, it may be prone to massive gallium precipitation or the precipitation position moving upward. In some cases, the energy threshold is the same in both the seed formation step and the expansion step. In this case, the pulse energy at the focal points P1 to P6 can be set equal (first energy setting). This allows the energy applied in six separate steps to be equal. This makes it possible to suppress massive gallium precipitation. Furthermore, there are also cases in which the energy threshold is higher in the expansion step than in the seed formation step. For example, there are cases in which the state is unstable until the seed of the modified region MA is formed, but the change stabilizes once the seed of the modified region MA is formed. In this case, the pulse energy at the focal point on the front side of the propagation direction TD can be set lower than the pulse energy at the focal point on the rear side of the propagation direction TD (second energy setting). This allows the peak output to be higher in the latter expansion step than in the former seed formation step. This makes it possible to efficiently expand the modified region MA. There are also cases where the energy threshold is higher in the seed formation step than in the expansion step. For example, this is the case when more energy is required to form the seeds of the modified region MA than to expand the modified region MA. In this case, the pulse energy at the focal point on the front side of the traveling direction TD can be made higher than the pulse energy at the focal point on the rear side of the traveling direction TD (third energy setting). This allows the peak output to be higher in the former seed formation step than in the latter expansion step. This makes it possible to efficiently form the seeds of the modified region MA.

[0048] The substrate manufacturing apparatus of this specification can measure the size of the modified region MA while forming one modified layer (FIG. 5, step S15). If the size of the modified region MA is smaller than the allowable range, the number of focusing points can be increased to increase the integrated amount of energy applied to the modified region MA (step S17). On the other hand, if the size of the modified region MA is larger than the allowable range, the number of focusing points can be decreased to decrease the integrated amount of energy applied to the modified region MA (step S18). In-situ feedback control makes it possible to form modified regions MA of appropriate sizes. [Example]

[0049] The substrate manufacturing apparatus 1a (FIG. 7) of the second embodiment differs from the substrate manufacturing apparatus 1 (FIG. 1) of the first embodiment in that it is provided with a plurality of laser light sources 21a and 22a. The same reference numerals are used to designate parts common to the substrate manufacturing apparatus 1 of the first embodiment, and descriptions thereof will be omitted.

[0050] The irradiation unit 13a includes laser light sources 21a and 22a. Focus points P1 to P3 are formed by modulating a pulsed laser PL1 output from the laser light source 21a. Focus points P4 to P6 are formed by modulating a pulsed laser PL2 output from the laser light source 22a. The pulsed laser PL1 and the pulsed laser PL2 have the same oscillation frequency and wavelength but different pulse widths. Therefore, the focus points P1 to P3 and the focus points P4 to P6 have different pulse widths. Furthermore, the spatial light modulator 23 modulates the pulsed lasers PL1 and PL2 so that the pulse energies of the focus points P1 to P6 are the same.

[0051] The pulse width can be set in various ways. For example, the pulse widths of the focal points P1 to P6 may be equal (first pulse width setting). The pulse width of the focal points P1 to P3 on the front side in the traveling direction TD may be smaller than the pulse width of the focal points P4 to P6 on the rear side (second pulse width setting). The pulse width of the focal points P1 to P3 may be larger than the pulse width of the focal points P4 to P6 (third pulse width setting). Since the peak output [W] is calculated by dividing the pulse energy [J] by the pulse width [s], when the pulse energy is constant, the peak output can be increased by reducing the pulse width.

[0052] (effect) As mentioned above, if the energy applied in a single laser irradiation exceeds the energy threshold, it is likely that a large amount of gallium will be precipitated. There are cases where the energy threshold is the same in both the seed formation step and the expansion step. In this case, the pulse widths at the focal points P1 to P6 can be set equal (first pulse width setting). This allows the energy applied in six separate steps to be equal.

[0053] There are also cases where the energy threshold is higher in the seed formation step than in the expansion step. In this case, the pulse width of the focal points P1 to P3 on the front side in the traveling direction TD can be made smaller than the pulse width of the focal points P4 to P6 on the rear side (second pulse width setting). This allows the peak output to be higher in the first half of the seed formation step than in the second half of the expansion step. This makes it possible to efficiently form seeds for the modified region MA.

[0054] There are also cases where the energy threshold is higher in the expansion step than in the seed formation step. In this case, the pulse width of the front focal points P1 to P3 can be made larger than the pulse width of the rear focal points P4 to P6 (third pulse width setting). This allows the peak output to be larger in the latter expansion step than in the former seed formation step. This makes it possible to efficiently expand the modified region MA.

[0055] It is difficult to change the pulse width when irradiating the same irradiation point with a pulsed laser a predetermined number of times. For example, consider the case in this embodiment where the pulse period is 0.02 ms and the pulsed laser is irradiated six times per irradiation point. In this case, the pulse width needs to be changed at a period of 0.1 ms, but it is difficult to perform such control on a laser light source. On the other hand, the substrate manufacturing apparatus 1a of this embodiment can be provided with multiple laser light sources with different pulse widths. This makes it possible to irradiate the same irradiation point with multiple focal points with different pulse widths.

[0056] Although the embodiments of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above.

[0057] (Variation) In the second embodiment, the laser light sources 21a and 22a have different pulse widths. However, this is not limiting and various parameters may be different. For example, the laser light sources 21a and 22a may have different wavelengths. By differentiating the wavelengths, it is possible to differentiate the absorption coefficients of GaN. Note that GaN absorbs lasers with wavelengths shorter than 362 nm, so the wavelength must be longer than this wavelength. Various wavelengths can be set. For example, the wavelengths of the focal points P1 to P6 may be equal (first wavelength setting). The wavelengths of the focal points P1 to P3 on the front side of the traveling direction TD may be longer than the wavelengths of the focal points P4 to P6 on the rear side (second wavelength setting). The wavelengths of the focal points P1 to P3 may be shorter than the wavelengths of the focal points P4 to P6 (third wavelength setting). Note that the wavelength setting to be used can be determined appropriately depending on the change in the absorption coefficient of GaN relative to the wavelength.

[0058] In this specification, the case where one of the pulse energy, pulse width, and wavelength is made different among the multiple focal points has been described, but this is not limited to this. Two or more of the pulse energy, pulse width, and wavelength may be made different. For example, the pulse energy of focal points P1 to P3 may be made smaller than the pulse energy of focal points P4 to P6, and the pulse width of focal points P1 to P3 may be made larger than the pulse width of focal points P4 to P6. This allows the peak output to be higher in the latter expansion step than in the former seed formation step.

[0059] Furthermore, the parameters that are made different among the plurality of focal points are not limited to pulse energy, pulse width, and wavelength, but may be various other parameters. For example, the pulse waveform may be made different.

[0060] The techniques described herein are not limited to gallium nitride (GaN) but can be applied to the formation of substrates of various compound semiconductors, such as aluminum nitride (AlN) and indium nitride (InN), among other nitride semiconductors.

[0061] The following numerical values ​​described in this specification are examples and are not limited to these values. That is, the number of scanning lines SL1 to SL6 in FIG. 3 is one example. The number of modified layers and substrate layers in FIG. 6 is one example. The values ​​of the pulse laser period, predetermined pitch PP, and peak output are one example. In the substrate manufacturing apparatus 1a of Example 2 (FIG. 7), the number of laser light sources is not limited to two, and may be three or more.

[0062] The technical elements described in this specification or drawings may exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technologies illustrated in this specification or drawings may achieve multiple objectives simultaneously, and achieving one of those objectives alone is technically useful. [Explanation of symbols]

[0063] 1, 1a: substrate manufacturing device 11: stage driving unit 12: stage 13: irradiation unit 14: measurement unit 15: control unit 21: laser light source 23: spatial light modulator 24: condenser lens 30: ingot MA: modified region P1 to P6: condenser points PP: predetermined pitch

Claims

1. a stage on which a semiconductor substrate can be placed; an irradiation unit capable of irradiating the semiconductor substrate placed on the stage with a pulse laser having a predetermined pulse period; a control unit capable of controlling the relative position of the stage and the irradiation unit; A substrate manufacturing apparatus comprising: the irradiation unit is capable of generating a plurality of light-converging points arranged in a straight line at a predetermined pitch; the control unit is capable of moving the relative position between the stage and the irradiation unit at a predetermined speed in parallel to a straight line on which the plurality of light-focusing points are arranged, The predetermined speed is a speed at which the distance that the plurality of focal points move in one period of the predetermined pulse period is the same as the predetermined pitch.

2. the irradiation unit includes a plurality of laser light sources, The substrate manufacturing apparatus according to claim 1 , wherein the plurality of focal points are generated by the plurality of laser light sources.

3. 3. The substrate manufacturing apparatus according to claim 1, wherein pulse energy at some of the plurality of focal points is different from pulse energy at other focal points.

4. 4. The substrate manufacturing apparatus according to claim 3, wherein the pulse energy of a focal point on a front side in a direction of movement of the plurality of focal points by the control unit is smaller than the pulse energy of a focal point on a rear side in the direction of movement.

5. 4. The substrate manufacturing apparatus according to claim 3, wherein the pulse energy of a focal point on a front side in a direction of movement of the plurality of focal points by the control unit is greater than the pulse energy of a focal point on a rear side in the direction of movement.

6. 6. The substrate manufacturing apparatus according to claim 1, wherein the pulse widths of some of the plurality of focal points are different from the pulse widths of the other focal points.

7. 7. The substrate manufacturing apparatus according to claim 6, wherein a pulse width of a focal point on a front side in a direction of movement of the plurality of focal points by the control unit is smaller than a pulse width of a focal point on a rear side in the direction of movement.

8. 7. The substrate manufacturing apparatus according to claim 6, wherein a pulse width of a focal point on a front side in a direction of movement of the plurality of focal points by the control unit is larger than a pulse width of a focal point on a rear side in the direction of movement.

9. 9. The substrate manufacturing apparatus according to claim 1, wherein the wavelengths of some of the plurality of focal points are different from the wavelengths of the other focal points.

10. 10. The substrate manufacturing apparatus according to claim 9, wherein the wavelength of the focal point at the front of the direction of travel in which the control unit moves the focal points is longer than the wavelength of the focal point at the rear of the direction of travel.

11. 10. The substrate manufacturing apparatus according to claim 9, wherein the wavelength of the focal point at the front of the direction of travel in which the control unit moves the focal points is shorter than the wavelength of the focal point at the rear of the direction of travel.

12. a measurement unit for measuring a modified region formed on the semiconductor substrate on the stage by the plurality of focusing points; 12. The substrate manufacturing apparatus according to claim 1, wherein the irradiation unit controls the number of the plurality of light-focusing points in accordance with a measurement result by the measurement unit.

13. the measuring unit is capable of measuring the size of the modified region, The substrate manufacturing apparatus according to claim 12 , wherein the irradiation unit controls the number of the plurality of light-converging points to be increased as the size of the modified region is smaller.

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